Currently, handheld electronic devices such as smart phones and tablet PCs usually have high definition (HD) video recording capabilities, and currently, many high-end smart phones have already been capable of recording smooth high-definition videos with a resolution of 1080p. Furthermore, since high-definition videos are becoming more and more popular, a large amount of high-definition videos are stored on many handheld electronic devices. However, since screens of the handheld electronic devices are small, advantages of high definition cannot be displayed when high-definition videos are played on the handheld electronic devices. Therefore, consumers are urgent to need a method for outputting high-definition videos into large screen display devices such as a television set, a projector, and a computer (PC).
A high-definition multimedia interface (HDMI) is an interface for transmitting uncompressed digital high-definition video/audio, and is forward and backward compatible with a digital video interface (DVI). The DVI only transmits video data, while the HDMI inserts multichannel audio data and status data in the intervals of bursts of video data of DVI. In data transmission, the HDMI uses the transition minimized differential signaling (TMDS) technology. The TMDS technology is a technology for transmitting signals by using a voltage difference between two pins (that is, differential transmission). The TMDS has four channels, in which the first three lines are transmission lines of YU (Pb) V (Pr) or seen as RGB transmission lines, and the fourth line a line for clock, so as to ensure a unified time sequence required in transmission. In general, the four lines are called a connection or a single-link. The maximum transmission rate per channel is 165 MHz (4.95 Gb/s), and a connection provides a transmission rate of 5 Gbps. After the MDS decoding, original data is encrypted based on high definition content protection (HDCP). In addition, 8b/10b differential signals are used to reduce EMI and increase accurate signal transmission rate, and 8-bit input signals are converted into 10-bit codes. Connectors of the HDMI interface have three physical specifications which are called Type A, Type B, and Type C respectively. Type A includes 19 pins, and definitions of each pin are shown in FIG. 1. As seen, six pins in total are used to transmit TMDS data and the six pins are connected to three pairs of differential transmission lines, and two pins are used to transmit TMDS clock signals; in addition, there are pins for power supply, shielding, grounding, control signal and so on. A Type A socket has a maximum width of 14 mm, and a height of 4.55 mm. The Type B has 29 pins, and the size is great. Similar to the Type A, a Type C has 19 pins and the only difference is the size. The size of a Type C socket is 10.5 mm×2.5 mm.
Obviously, the size of the Type A is too great for handheld electronic devices, and the Type C is suitable for handheld mobile devices. However, 19 pins are disposed in a small size of the Type C, which has a much higher requirements on the accuracy for manufacturing an interface, increases manufacturing costs, and reduces the reliability of the interfaces due to high-density wiring. In fact, the number of pluggable times of a Type C HDMI connector is much smaller than that of other connectors with a similar size, for example, a micro universal serial bus (Micro USB) connector.
Furthermore, since the size of handheld electronic devices themselves is small, if more interfaces are added, the space is occupied in one aspect and the manufacturing cost is also increased in another aspect.